How stem cells produce an ordered series of diverse progeny according to their age, or "temporal identity", is a major unanswered question in biology. Identification of mechanisms that control temporal identity is crucial for understanding the regulation of fate potential in human stem cells and for understanding oncogenesis due to stem cell defects. In the Drosophila brain, neural stem cells that produce the mushroom body (MB) and the antennal lobe projection neurons (AL-PNs) are temporally specified to make distinct progeny, providing an ideal system for studying temporal identity regulation. This research project is designed to identify the changes in gene expression that occur during the generation of unique MB and AL-PN cells and to identify the temporal identity factors that control the generation of unique progeny. This will be accomplished using: (1) A novel method for cell-specific mRNA purification to analyze gene expression during the development of these two lineages. (2) A mosaic genetic screen to identify genes necessary for the specification of AL-PN temporal identity. (3) Loss-of-function and gain-of-function assays to determine the temporal identity phenotypes of genes identified using the first two approaches. [unreadable] [unreadable]